Full Idea
It is not necessary for what moves things to be itself moving. For a thing can be moving in two ways - with reference to something else, or intrinsically. A ship is moving intrinsically, but sailors move because they are in something that is moving.
Gist of Idea
Movement can be intrinsic (like a ship) or relative (like its sailors)
Source
Aristotle (De Anima [c.329 BCE], 406a03)
A Reaction
I love the way that Aristotle is desperate to explain the puzzle of movement, yet we just take it for granted. Very illuminating about puzzles. Newton's First Law of Motion.
Book Reference
Aristotle: 'De Anima (on the psuche)', ed/tr. Reeve, C.D.C. [Hackett 2017], p.9